<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>

  <style>
    #app{
      width: 500px;
      height: 100px;
      border: 1px solid red;
      /* text-align: center; */
      /* display: flex;
      justify-content: center; */
    }
    #app div{
      width: 100px;
      height: 100px;
      float: left;
      /* display: inline-block; */
    }
    .one{
      background-color: pink;
    }
    .two{
      background-color: yellow;
    }
    .three{
      background-color: blue;
    }

    #ver{
      width: 200px;
      height: 200px;
      background-color: pink;
      /* line-height: 200px; */
      /* vertical-align: middle; */
    }
  </style>
</head>
<body>
  <div id="app">
    <div class="one"></div>
    <div class="two"></div>
    <div class="three"></div>
  </div>
  <div id="ver">
    <div class="four">123</div>
    <div class="four">123</div>
    <div class="four">123</div>
  </div>
</body>
</html>